The cause of arthritis and joint disease processes is multiple. Inflammatory joint disease may be related to stimulation of the immune system to the normal joint tissues. Similarly the various collagen diseases can stimulate the inflammatory process i.e. systemic lupus, erythemtosis. Rheumatoid arthritis and osteoarthritis are also examples of disease processes which affect the joint. Infection with bacteria, viruses and fungus can initiate a degenerative process. Tumors both primary and metastatic can invade the joint space and cause destruction. In all of these processes the mechanism is quite similar. Inflammatory cells invade the synovial lining of the joint. A pannus forms and eventually destruction of the joint ensues. The present invention describes a method to stop and/or measureably alter the process before destruction of the joint occurs, thereby preserving the normal joint.
The electromagnetic field interacts with joint tissues in several ways. There are displacement currents due to the drift of electrons, polarization of atoms or molecules to produce dipoles and the interaction with dipoles already present. The coupling of electromagnetic energy to the joint tissues depends on the electrical conductivity (.delta.) and the dielectric constant (.epsilon.). The power imparted to the joint issues depends on the square of the amplitude of the field and the coupling constant to the joint tissues. The dielectric properties of the material depend on its composition and structure (i.e. ions, polar molecules, etc.).
In general: EQU .epsilon.=.epsilon.'-j.epsilon."
where
.epsilon.'=real component related to energy stored in the material in electric fields PA1 .epsilon."=imaginary component related to loss in the form of heat=.delta.2nf.epsilon..sub..omicron. PA1 .delta.=conductivity so that conductivity is related to the amount of heat loss. Often as there is an increase in frequency, .epsilon.' decreases due to less ordering and .epsilon." increases.
In joint tissues a plot of the dielectric constant as a function of frequency often shows three dispersions. Each dispersion is related to a specific phenomenon. The oc dispersion (at.apprxeq.80-100 Hz) is due to the interaction of the charges on the cell surface with the ions in solution and the impedence of the membrane system.
The B dispersion (at.about.50 KHz) is related to the cell membrane's insulation of the H.sub.2 O. Above 10 GHz the .gamma. dispersion is due to the H.sub.2 O and electrolyte solution. To overcome these problems the common practice is to use a frequency &gt;&gt;1 KHz to short out the membrane effects and to deliver energy to the cytoplasm.
Consequently, frequencies greater than 1 KHz and usually greater than 1 MHz are utilized to overcome problems with the cell membrane and deliver energy to the cell. Traditionally, frequencies of 13 MHz or 2450 MHz are used. However, the problem remains that at these high frequencies not only are the joint reactive cells affected but the normal cells are also affected and consequently one is limited in the amount of energy which can be delivered to the reactive joint cells.
The present invention seeks to overcome this problem by modifying the intracellular environment to allow the use of lower frequencies, if possible, and to enhance the effect in the reactive joint cells without affecting the normal cells.